# 【LeetCode】 14. Longest Common Prefix

## Description
> Write a function to find the longest common prefix string amongst an array of strings.
> If there is no common prefix, return an empty string "".

> 寫一個function在字串陣列中尋找最長共同前字串。
> 如果沒有共同的前字串，回傳空字串""。

## Example:

Example 1:

Input: ["flower","flow","flight"]
Output: "fl"


Example 2:

Input: ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

## Solution

* 把第一個字串的字當作標準，去判斷後面的字串是不是一樣的字。
* 比較需要特別注意的是，陣列為空陣列、或是索引值超出字串範圍。

### Code

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        string str;
        int count = 0;
        while(1)
        {
            bool isSame = true;
            if(strs.size()==0 || strs[0].size()<count)
                break;
            char c = strs[0][count];
            for(int i=1;i<strs.size();i++)
            {
                if(strs[i].size()<count||strs[i][count] != c)
                {
                    isSame = false;
                    break;
                }
            }
            if(isSame)
                str += c;
            else
                break;
            count++;
        }
        return str;
    }
};

###### tags: `LeetCode` `C++`